[engine] Enable cppcoreguidelines-pro-type-member-init clang-tidy check - #194576

…ck (flutter#194576)

This PR enables a linter check that flags uninitialized variables. We
ran into a problem when flutter#194540
landed which was the result of uninitialized variables. This should
catch those kinds of issues earlier. Most of this PR is generated by
clang-tidy's fix operation, gemini operated where that failed.

Description from gemini:

> flutter#194540 fixed uninitialized counters in `DlComplexityPathReceiver`
that caused a flaky `DisplayListComplexity.DrawShadow` failure. None of
the clang-tidy checks we had enabled flag uninitialized members:
`modernize-use-default-member-init` only rewrites existing constructor
initializers, and the static analyzer gives up once the object is passed
by reference to an out-of-line call.
> 
> This enables `cppcoreguidelines-pro-type-member-init` (with
`UseAssignment: true`) and fixes the existing violations:
> 
> * Scalar/pointer/enum members get default member initializers (`= 0`,
`= nullptr`, or an explicit enumerator).
> * Uninitialized locals of trivially-constructible record types
(`FragInfo`, `PointerData`, `struct stat`, ...) are value-initialized
with `{}`.
> * Union-based types where the check reports false positives
(`Vector3`/`Vector4`, `HalfVector*`, `Quaternion`, `Shear`,
`SaveLayerOptions`) are wrapped in `NOLINTBEGIN/END` with an
explanation.
> 
> Default member initializers don't change object size or layout. The
only runtime cost is a few stores at construction, and most of those are
dead stores the optimizer removes.
> 
> Verified locally: `--lint-all` with this check is clean on
`host_debug_unopt_arm64` (macOS) and `android_debug_unopt_arm64`, and
both build. Linux host and iOS simulator lint variants will be checked
by CI.
> 

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
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- [x] I read the [AI contribution guidelines] and understand my
responsibilities, or I am not using AI tools.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [ ] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant in-code documentation (doc comments with
`///`).
- [x] If this PR introduces a new feature or capability, I created and
linked a website documentation issue or PR in [flutter/website] (or
verified none is needed).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [ ] All existing and new tests are passing.

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[Features we expect every widget to implement]:
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[Data Driven Fixes]:
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